Elisabeth Rungger-Brändle

Distribution of vimentin and desmin filaments in smooth muscle tissue of mammalian and avian aorta

Abstract The presence of intermediate filament proteins in vascular tissue cells has been examined by immunofluorescence microscopy on frozen sections of the aortic wall of diverse vertebrates (rat, cow, human and chicken) and by gel electrophoresis of cytoskeletal proteins from whole aortic tissue or from stripped tunica media of cow and man. Most cells of the aortic wall in these species contain vimentin filaments, including smoooth muscle cells of the tunica media. In addition, we have observed aortic cells that are positively stained by antibodies to desmin. The presence of desmin in aortic tissue has also been demonstrated by gel electrophoresis for rat, cow and chicken. In aortic tissue some smooth muscle cells contain both types of intermediate filament proteins, vimentin and desmin. Bovine aorta contains, besides cells in which vimentin and desmin seem to co-exist, distinct bundles of smooth muscle cells, located in outer regions of the tunica media, which contain only desmin. The results suggest that (i) intermediate-sized filaments of both kinds, desmin and vimentin, can occur in vascular smooth muscle in situ and (ii) smooth muscle cells of the vascular system are heterogeneous and can be distinguished by their intermediate filament proteins. The finding of different vascular smooth muscle cells is discussed in relation to development and differentiation of the vascular system.

Cytoskeletons of retinal pigment epithelial cells: Interspecies differences of expression patterns indicate independence of cell function from the specific complement of cytoskeletal proteins

SummaryIn vertebrate tissue development a given cell differentiation pathway is usually associated with a pattern of expression of a specific set of cytoskeletal proteins, including different intermediate filament (IF) and junctional proteins, which is identical in diverse species. The retinal pigment epithelium (RPE) is a layer of polar cells that have very similar morphological features and practically identical functions in different vertebrate species. However, in biochemical and immunolocalization studies of the cytoskeletal proteins of these cells we have noted remarkable interspecies differences. While chicken RPE cells contain only IFs of the vimentin type and do not possess desmosomes and desmosomal proteins RPE cells of diverse amphibian (Rana ridibunda, Xenopus laevis) and mammalian (rat, guinea pig, rabbit, cow, human) species express cytokeratins 8 and 18 either as their sole IF proteins, or together with vimentin IFs as in guinea pig and a certain subpopulation of bovine RPE cells. Plakoglobin, a plaque protein common to desmosomes and the zonula adhaerens exists in RPE cells of all species, whereas desmoplakin and desmoglein have been identified only in RPE desmosomes of frogs and cows, including bovine RPE cell cultures in which cytokeratins have disappeared and vimentin IFs are the only IFs present. These challenging findings show that neither cytokeratin IFs nor desmosomes are necessary for the establishment and function of a polar epithelial cell layer and that the same basic cellular architecture can be achieved by different programs of expression of cytoskeletal proteins. The differences in the composition of the RPE cytoskeleton further indicate that, at least in this tissue, a specific program of expression of IF and desmosomal proteins is not related to the functions of the RPE cell, which are very similar in the various species.

An actin-destabilizing factor is present in human plasma.

Plasma and serum of humans or experimental animals contain a factor which destabilizes F-actin. The factor has no DNAse or thrombin activity and after incubation with F-actin does not modify the position of the actin band on a SDS polyacrylamide gel. Hence it probably depolymerizes F-actin.

Bilateral Acute Retinal Necrosis (BARN): Identification of the Presumed Infectious Agent

We describe histopathologic features of an enucleated eye of a patient suffering bilateral acute retinal necrosis (BARN). Retinal tissue was found focally degenerated, and the choroid massively enlarged by lymphoid-like agranular cells. An association of the disease with a viral infection could be demonstrated by (a) the presence of virus particles of the herpesvirus type in retinal tissue, (b) the transmission of the infected principle to human embryo fibroblast cultures, and (c) the visualization of CMV-antigens by immunofluorescence microscopy in such infected cultures. Slow growth of the virus in vitro and the presence of CMV-antigens after infection indicate that the herpesvirus involved in BARN was of the type CMV. On the basis of these findings we propose a guideline for therapy.

Association of specific cell-surface glycoproteins with a triton X-100-resistant complex of plasma membrane proteins isolated from T-lymphoma cells (P 1798)

A non-ionic detergent-resistant complex of membrane-associated proteins and cell-surface glycoproteins has been isolated by gel filtration and isopyknic centrifugation of purified plasma membranes from the murine T-lymphoma P 1798. This complex elutes as a high molecular weight peak (greater than 15 X 10(6) D) and contains two specific sets of (1) cell-surface glycoproteins; (2) membrane-associated proteins. The cell-surface glycoproteins consist of two vectorially labelled major components present in a fixed molar ratio: The Thy-1 glycoprotein and a non-H-2 glycoprotein of 55 kD. Minor but significant amounts of the class I histocompatibility antigen Qa-2 are also contained in the detergent-resistant complex. The membrane-associated proteins are not vectorially labelled, and form a complex group of proteins in the 30-70 kD range. Since actin is not detectable among these polypeptides, they probably constitute a plasma membrane-associated structure that is distinct from actin-containing, submembranous cytoskeletal elements.

Retinal patterning by Pax6‐dependent cell adhesion molecules

Long‐standing evidence gained from Pax6 mutant embryos pointed to an involvement of Pax6‐dependent cell adhesion molecules in patterning the central nervous system and, in particular, the retina. However, direct evidence for such pathways remained elusive. We here present direct evidence that knockdown of Pax6 expression by morpholino antisense molecules in Xenopus embryos and knockdown of maternal N‐cadherin (mNcad), N‐cadherin (Ncad) and neural cell adhesion molecule (NCAM) produce similar phenotypes. Eye formation is reduced and retinal lamination is heavily disorganized. In Pax6 knockdown embryos, the levels of mRNAs coding for these cell adhesion molecules are markedly reduced. Overexpression of Pax6 efficiently rescues the phenotype of Pax6 knockdown embryos and restores expression of these putative target genes. Rescue of Pax6‐deficiency by the putative target gene mNcad moderately rescues eye formation. The promoters of the genes coding for cell adhesion molecules contain several putative Pax6 binding sites, as determined by computer analysis. Chromatin immunoprecipitation shows that, in embryonic heads, Pax6 binds to promoter regions containing such predicted binding sites. Thus, several cell adhesion molecules are direct target genes of Pax6 and cooperate in retinal patterning.

Role of sialic acid and sulfate groups in cervical mucus physiological functions: study of Macaca radiata glycoproteins

The influence of charged groups in glycoproteins was investigated to assess their effect on the physiological functions of bonnet monkey cervical mucus. The macromolecular glycoproteins from peri-ovulatory, midcycle phase cervical mucus were treated with Pronase, trypsin and chymotrypsin and the enzyme-resistant glycoproteins purified by gel filtration on Sepharose 4B and a high molecular weight component containing carbohydrates, proteins and sulfate groups was recovered in high yield. This material still reacted with an antiserum directed against purified midcycle glycoprotein but not against another antiserum directed against luteal phase purified glycoproteins. Upon treatment with Pronase, trypsin and chymotrypsin, asialoglycoproteins and desulfated asialoglycoproteins released fragments of low molecular sizes, none of which reacted with the anti-midcycle glycoprotein antiserum. Cervical mucus collected from the estrogenic phase displayed a morphology supporting sperm migration, and this mucus retains the same morphology and reacts with the anti-midcycle glycoprotein antiserum following mild treatment with sialidase and subsequently with Pronase. These results imply that charged carbohydrate groups help maintain the structural and functional integrity of the mucus glycoprotein in its biological environment.

Abnormal microtubules in testes of the mutant l(3)pl (lethal-polyploid) of Drosophila hydei, cultured in vivo.

Abstract During early spermatid elongation, at which time germ cells of the mutant l(3)pl (lethal-polyploid) of Drosophila hydei are entirely blocked in their differentiation [16], the microtubular system displays numerous abnormalities on the ultrastructural level. Unstable localization of the otherwise normal centriole, fractionation of the nebenkern, and lack of both nuclear and cellular elongation reflect a general disorganization in cellular arrangement. Moreover, in the growing flagellum, the central tubules are missing. The cytoplasmic microtubules are reduced in number and show various structural abnormalities. Less than one-third have a normal cylindrical cross-section. Single tubules or doublets with one or several side projections of varying lengths are observed, the most frequent representing an α-shape. Cross-bridged tubules may form short chains. The similarity of the observed malformations to the effects of antimitotic drugs suggests that the gene l(3)pl acts at the level of microtubular assembly.

Filamentous structures containing a keratin-like protein in spermatozoa of an insect, Bacillus rossius

Spermatozoa of a phasmid insect, Bacillus rossius , contain, in the whole length of the tail, two longitudinal crystalline bodies flanking the axoneme and made up of a texture of 10-nm filaments. These filaments are resistant to nonionic detergent extraction (Triton X-100) and appear particularly evident after deep-etching. SDS-polyacrylamide gel electrophoresis, immunoblotting, and immunochemical methods, at both the light and the electron microscopic level, show that they share antigenic determinants with the vertebrate cytokeratins. All these properties suggest that these filaments are members of the cytokeratin family. The occurrence of keratin in invertebrates is discussed.

Morphogenetic deficiencies in transplanted gonadal anlagen of the mutant l(3)pl (lethal-polyploid) in Drosophila hydei☆

Abstract Larval gonads of Drosophila hydei , homozygous for the lethal gene l(3)pl (lethal-polyploid), were cultured in normal hosts. Ovaries of the late third larval instar were implanted into metamorphosing larvae. These can attach to the gonoduct system of the host and transform into adult ovarian structures but the spectrum of their capacity to differentiate varies largely. In favourable cases mature oocytes can be formed which are fertile. More frequently mitotic disturbances in the follicle cells and cystocytes lead to the formation of abortive egg chambers and abnormally shaped oocytes. Testes of the middle third larval instar were cultured for 2 weeks in adult females. Primary spermatocytes are able to sustain meiotic divisions and form early spermatids, even though the occurrence of fractionated nuclei in post-meiotic germ cells indicates defective meiotic divisions. Post-meiotic differentiation is blocked in mutant spermatids which fail to elongate. The mutant gene l(3)pl thus, not only affects cell divisions, but also interacts in certain cytodifferentiation processes such as spermatid elongation and egg shaping. All cellular processes found so far to be abnormal in mutant tissues involve microtubular function. This suggests that the gene l(3)pl interacts with the microtubular system and several aspects of this interpretation are discussed.